Brian Dunning's FileMaker Custom Functions

ValStdDevS ( ValueList ; ArithMeanValue )

Gives the standard deviation of a sample, where the set of numbers are in a value list

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Bill Thurmes   Bill Thurmes

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  Sample input:
ValStdDevS ( "5¶8¶24¶3¶6" ; ValueMean ( "5¶8¶24¶3¶6" ) )
ValStdDevS ( "5" ; ValueMean ( "5¶8¶24¶3¶6" ) )
ValStdDevS ( "5¶a¶24¶3¶6" ; ValueMean ( "5¶a¶24¶3¶6" ) )
  Sample output:
? --> divides by N-1; N=1; so, divide by 0
9.44986... ['a' resolves as 0]

  Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

The native StDev function in FileMaker only works on fields, but it is often more efficient to work with value lists and do all calculations in memory. This is particularly true when you use ESQL, where the answer is returned as a value list. The ValStdDevS function gives the standard deviation of a set of numerical values in a ¶-delimited value list. This uses the square root of (the sum of squares divided by N-1); for some uses, ValStdDev (which uses N) is more appropriate. One caveat: if a non-numerical value is used, it is evaluated as 0.



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